The 1998–99 George Washington Colonials men's basketball team represent George Washington University as a member of the Atlantic 10 Conference during the 1998–99 NCAA Division I men's basketball season.

The team was coached by Tom Penders and played their home games at the Charles E. Smith Athletic Center.

The Colonials finished atop the regular season conference standings.

After being knocked out in the semifinal round of the A-10 tournament, GW received an at-large bid to the 1998 NCAA tournament as No.

6 seed Indiana, 108–88,[1] to finish with a record of 20–9 (13–3 A-10).